Zinc-silver accumulator



April 29, 1952 H. G. ANDRE ZINC-SILVER ACCUMULATOR Filed Dec. 20, 1948 G15-CELLOPHANE E m m R 0 E u w E l Q .w me 3 ..............m....,..unu...Mnwm

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lNvENToR HENRI G. ANDRE AGENT Patented Apr. 29, 1,952

ZINC SILVER ACCUBIULATOR Henri G. Andr, Montmorency, France, assgnor to Yardney International `Corp., New York, N. Y., a corporation of New York Application December 20, 1948, Serial No. 66,291A In France July 28, 1948 (Cl. 13G-6) 7 Claims.

1 'My invention has for its object improvements in zinc-silver accumulators wherein the cycle of operation is designed in a manner such that the discharge brings the negativeV electrode from its metal state to the zinc oxide or zinc hydroxide state while the charge brings it back from the state'of oxide or vhydroxide to its reduced metallic zinc state, no modication occurring in the electrolytic solution by reason of its preliminary" saturation as to zincic salts.'

Hitherto a'zinc carrier was used part of which was adapted to be transformed into an oxide, whether hydrated or otherwise.

In this technique in the case of a protracted discharge, a total oxidation of the zinc risks rendering it less suitable as a support while the amount of oxide formed risks becoming abnormally bulky through crystallisation with the electrolyte water which leads to an inadmissible com'- pression and expansion thereof inside the cell.

In order to define an upper limit forthis oxidation during a protracted discharge, I have provided according to my present invention the substitution, for an undefined mass of zinc in excess, of a homogeneous mass of zinc oxide that may be easily distributed round the positive silver electrode and of which it is possible to calculate beforehand the zinc contents that should correspond to the electro-chemical equivalent, transformed by thev discharge.y

The current is then fed to this homogeneous mass through any suitable means such as a metal grid that cannot dissolve in the electrolyte "(e. g.

potash) and that may be easily brought to a voltage corresponding to the zinc potential, said grid being made for instance of brass, copper, silver, etc.

The zinc oxide may be admixed with potash or a suitable alkaline composition so as to form a paste in which is dipped the positive electrode N that is previously protected by a Wrapper made of viscose foil such as cellophane.

According to a preferred procedure, I avoid the introduction into the positive compartment of any nnely subdivided zinc oxide by using a negative electrode the structure of which is identical with that of pulverulent silver and by pasting the metallic grid therewith and then packing the whole arrangement in the same manner as the positive electrode made of pulverulent silver. In an alternative, the negative electrode is a zinc plate wrapped inside a viscose foil Wrapper.

The two electrodes thus pasted and suitably packed are juxtaposed in intimate relationship without any risk of the actual silver and zinc oxide powders coming into contact.

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This perfect separation provides an excellent conservation of the charge conditions in open circuit together with complete regularity in the structure of the elements thus constituted which would be very diflicult to obtain with the prior structures proposed.

The accompanying drawing shows by way of example an'embodiment of a cell enclosing two packed electrodes of which the positive cell has a pulverulent silver base and the negative one a pulverulent zinc oxide base or again the positive electrode may have a pulverulent silver peroxide base and the negative one a pulverulent zinc base if it is desired to obtain a charged cell.

Fig. ,1A illustrates cross-sectionally a simple "cell,

outside the block of electrodes appearing crosssectionally in Fig. 1A.

Fig. 2 is a' cross-section of a system of several cells inserted in parallel in the same container.

As shown in Fig. 1A the silver lead I feeds current to the pulverulent silver electrode 3 in which is a silver lead. The lead .2 feeds current to the pulverulent zinc 'oxide electrode 4 through the grid 5, made of a metal that is insoluble in the electrolyte'.

The pulverulent silver 3 isV held inside a wrapper .of cellophane t while the pulverulent zinc oxide is .held inside a cellophane Wrapper 6". The outer wrappers l Vand 8 protect respectively the wrappers 6 and Bf that are also protected inwardly by the wrappers 9 and I0. Rubber tubes H "and l2 protect and insulate the connecting wires i and 2.

Figs. 1A and 1B show that with such a double protection no particle of active material may pass from the positive compartment into the negative compartment or reversely.

Turning to Fig. 2 showing a system of parallel cells inside a common container I5, the inner conductibility is ensured through the mere juxtaposition of the positive packages l and of negative packages 8 that are impregnated with the electrolyte filling the container l5. The groups of wires i and 2 are connected with the terminals I3 and i4 in parallel.

It is possible to obtain the electrodes shaped as illustrated by packing at the powders and feeding leads thereto inside cellophane sheets, superposing the ila-t packages thus Obtained and folding the superposed packages for introducing them into the container.

The risk of the electrolyte being dissociated during the final stage of the charge, the zinc beingprecipitated out of its solution 'at'such a momentso that the excess voltage forming an indication of the end of the charges appears after a certain destruction of the cell is already under Way-is prevented by making the positive electrode give out the signal of the end of the charge 5 by reason of. an excess of active negative material that remains 'in place during the Whole operation.

Furthermore, iurther and automatic safety is` obtained through the fact that the electrodes Wrapped according to the invention retain-the gases at the end of the charge so .thattheelectrodes are enclosed inside agaseoussheath.and.A the charging current is almost completely cut'o.`

It should be noticed that inV accumulators acl5 cording to the invention, it isvery easy `to'lreepthe cell in its discharged state by reason ofthe fact that the metal on the negative side is naturally in its oxidized state and cannot therefore be deteriorated throughV oxidation.

What I claimfis:

l. In' an electrochemical generator of energy,- in combination, a-positiveelectrode and. a negative electrode, at least one of said electrodes comprising an electrochemically activeinaterial andv r an `electrolyte-permeable insulating` envelopeenclosingsaid material, said envelope-being folded substantially in the-form of a -U with upstandingarms, the other of Asaid electrodes beingv eniolded bythe'arms'oiY the U. 3 2.'In an electrochemical vgenerator of energy; inV conlbination, a positive electrode and a, negativeelectrode; each of Vsaid electrodes comprising an electrochemically'active material and an elec'- trolyte-perrneable insulating envelope enclosing:`A

' ingtzincfas Vanactive material, .a positive electrode in said electrolyte containing av metal more electropositive than .zinc as-an active material, the active .material 4of 'at least one of 'said 'electrodesb'eingfin comminuted formfan electrolytebattery.

51Any electric stoi'age battery according to claims-1 :Wherein-ssaidamore electropositive metal is. silver.

6.-y An electric e storage battery comprising a container, ,an alkaline electrolyte in said contai-ner,` said electrolyte being saturated with zinc, a-negative electrode in said electrolyte containingzinc in comminuted form, a rst electrolytepermeable envelope of regenerated cellulose enclosingfsaidcomminutedizinc, a positiverelectrode in .said-electrolytexcontaining., an electrochemi v cally active..p0wder,rmore.electropositivethan.

zinc, ,a .secondelectrolyte-permeable. envelope of' insulating materialenclosing..saidpowder, eachotsaicLenvelopes,being` foldedtsubstantially .in4 .the form. a.U with. upstanding..arms, the arms. .ofA one.oi.said envelopes ,enioldingf the other, off-said envelopes..t andi. meansincluding, said, container.- maintaining said envelopes =..umier-4v compression,

0 thereby regulating. .the sii.'e.f,of. .the.Y pores =thereof and enablingrepeatedrecharging .of thebattery.V

7. An electric storage: battery,A accordinggto.. claim 6l ,wherein ,said electrochemically; active powder isCOmmin-uted silver..

HENRIYLG: ANDR-.fVr

REFERENCES; CITED. y-

The following :references are of frecord-"in: the f UNITEDSTATESQPA'IENTS.

Number# Number- 

1. IN AN ELECTROCHEMICAL GENERATOR OF ENERGY, IN COMBINATION, A POSITIVE ELECTRODE AND A NEGATIVE ELECTRODE, AT LEAST ONE OF SAID ELECTRODES COMPRISING AN ELECTROCHEMICALLY ACTIVE MATERIAL AND AN ELECTROLYTE-PERMEABLE INSULATING ENVELOPE ENCLOSING SAID MATERIAL, SAID ENVELOPE BEING FOLDED SUBSTANTIALLY IN THE FORM OF A U WITH UPSTANDING ARMS, THE OTHER OF SAID ELECTRODES BEING ENFOLDED BY THE ARMS OF THE U. 